SCIENCE, INVENTION, DISCOVERY. 



313 



main so suspended. This minimum tempera- 

 ture is called the dew point. During the day- 

 time, especially if there has been sunshine, a 

 good deal of aqueous vapor is taken into sus- 

 pension in the atmosphere. If the tempera- 

 ture in the evening now falls below the dew 

 point, which after a hot and calm day gener- 

 ally takes place about sunset, the vapor which 

 can be no longer held in suspension is de- 

 posited on the surface of the earth, sometimes 

 to be seen visibly falling in a fine mist. An- 

 other form of the phenomenon of dew is as 

 follows : The surface of the earth, and all 

 things on it, and especially the smooth sur- 

 faces of vegetable productions, are. constantly 

 parting with their heat by radiation. If the 

 sky is covered with clouds, the radiation sent 

 back from the clouds nearly supplies an equiv- 

 alent for the heat thus parted with ; but if the 

 sky be clear, no equivalent is supplied, and 

 the surface of the earth and things growing on 

 it become colder than the atmosphere. If the 

 night also be* calm, the small portion of air 

 contiguous to any of the surfaces will become 

 cooled below the dew point, and its moisture 

 deposited on the surface in the form of dew. 

 If the chilled temperature be below 32 degrees 

 Fahrenheit, the dew becomes frozen, and is 

 called hoar-frost. The above two phenomena, 

 though both expressed in our language by the 

 word " dew " which perhaps helps to lead 

 to a confusion of ideas on the subject -are 

 not necessarily expressed by the same word. 

 For instance, in French, the first phenomenon 

 --the falling evening dew is expressed by 

 the word serein; while the latter the dew 

 seen in the morning gathered in drops on the 

 leaves of plants or other cool surfaces is ex- 

 pressed by the word rose'e. Similar to rosee is 

 the moisture which condenses on the outside 

 surface of pitchers or glasses of ice-water. 

 The air in immediate contact is cooled below 

 the dew point and deposits the suspended 

 moisture. 



Dictionary. A standard dictionary of 

 the Chinese language, containing about 40,- 

 000 characters, most of them hieroglyphics, or 

 rude representations somewhat like our signs 

 of the zodiac, was perfected by Pa-out-she, 

 who lived about 1100 B. C. Cyclopedias were 

 compiled in the fifteenth and sixteenth cen- 

 turies. The first dictionary of celebrity, per- 

 haps the first, is by Ambrose Calepini, a Ve- 

 netian friar ; it is in Latin ; he wrote another 

 in eight languages, about A. I). 1500. Cham- 

 bers's Cyclopedia, the first dictionary of the 

 circle of the arts and sciences, was published in 

 1728. The English dictionary by Samuel John- 

 son appeared in 1755. Noah Webster's great 

 American dictionary of the English language 



in two volumes was published at New Haven 

 in 1828. Worcester's dictionary appeared in 

 1860. Harper's Latin Dictionary (founded 

 upon Andrews's translation of Freund's Latin- 

 German lexicon), adopted as the standard 

 authority in English and American universi- 

 ties, was published in 1879. 



Discovery of Gold in California. 

 On January 19, 1848, John W. Marshall 

 was building a mill for himself and Sutter on 

 the south fork of the American River, fifty- 

 four miles east of Sutter's Fort. This mill, it 

 was expected, would supply the ranches and 

 settlements with pine lumber. On this par- 

 ticular morning Marshall picked up from the 

 bed-rock of the race of the mill a small piece 

 of yellow metal which weighed about seven- 

 teen grains. It was malleable, heavier than 

 silver, and in all respects resembled gold. 

 Marshall showed the piece in the afternoon to 

 those who were working at the mill. The re- 

 sult of the discussion which ensued was the 

 rejection of the gold theory. Marshall, how- 

 ever, was not satisfied, and afterward tested it 

 with nitric acid, and found it was actually 

 gold. He discovered pieces like it in all the 

 surrounding gulches wherever he dug for it. 

 The news of the discovery soon spread, and 

 iu April reports of the find were published. 



Diving 1 Bells. The principle of the div- 

 ing bell is extremely simple, and can be seen 

 by pressing any hollow vessel mouth down- 

 ward into water. Although some species of 

 diving bell was probably used in the time of 

 Aristotle for it is recorded that divers took 

 with them a vessel which enabled them to- re- 

 main under water and in mediaeval times, it 

 was not until about 1715 that any practical 

 method of supplying the bell with air while 

 under water was discovered. About that year 

 this want was met by a Doctor Halley. He 

 used two water-tight barrels, each supplied 

 with a hose, also attached to the diving bell, 

 and these, attached to heavy weights, were 

 dropped on each side of the bell, and the 

 diver could, therefore, remain under water ap 

 long as the air supplied by the barrels was fit 

 to breathe. The diver's cap, which was made 

 of metal and fitted with a tube for conveying 

 air to it from the bell, so that the wearer 

 could leUve the bell and walk around the bot- 

 tom of the sea, was soon after devised by the 

 same inventor. In 1779, the air pump, which 

 forced down air from above, was applied to 

 diving bells by an engineer named Smeaton. 

 The most practical bell in use at present is a 

 sort of submarine boat, called the Nautilus, 

 with double sides, between which water is 

 forced to cause the boat to descend and air to 

 cause it to rise. 



